Pseudomonas infection is an underappreciated cause of morbidity and mortality. Nosocomial infections can be life-threatening in immunocompromized populations, cancer patients, the elderly, and patients with cystic fibrosis. Physicians try to protect patients with antibiotic therapy, but the bacteria quickly develop antibiotic resistance. A complementary approach to antibiotic therapy is therefore urgently needed, and one such approach is vaccination. Our long-range goal is to develop vaccines that protect against Pseudomonas lung infection. We have developed two effective outer membrane protein F (OprF)-based vaccines that protect against both nonmucoid and mucoid Pseudomonas phenotypes. These vaccines are called F/I and F/HG. The F/I vaccine consists of three biolistic inoculations of naked DNA sequences for the fusion protein OprF/l. The F/HG vaccine uses a prime-boost strategy with two biolistic inoculations of naked DNA-oprF sequences followed by an intramuscular booster containing the chimeric influenza virus HG10-11. Each vaccine appears to induce a polarized immune response. The F/I vaccine induced antibody-mediated immunity (AMI) while F/HG induced cell-mediated immunity (CMI). Insufficient information is available regarding the immune mechanisms whereby Pseudomonas infection is controlled or how Pseudomonas vaccines work. AMI in pulmonary Pseudomonas infection is believed to be important, but the definitive mechanism for clearance is unknown. We propose to define the mechanisms of antibody protection by identifying antibody isotypes and serum cytokines in infected and F/I-immunized mice that are immune-intact or immune-deficient. Likewise, the role of CMI in Pseudomonas pneumonia is poorly understood. Our F/HG vaccine will allow us to define the mechanism(s) of Pseudomonas-specific, cell-mediated protection in the lungs of infected and immunized mice that are immune-intact or immune-deficient. Defining these mechanisms will allow us to rationally modify immune responses to protect more effectively against pulmonary Pseudomonas infection. As researchers delineate the immune responses to pulmonary Pseudomonas infection in humans, we will be uniquely positioned to modify our vaccines to induce specific Th-1 or Th-2 responses. These rationally designed vaccines tested in a pulmonary chronic infection model will provide guiding principles to prevent and treat more effectively Pseudomonas pneumonia in humans. [unreadable] [unreadable] [unreadable]